Merchants had to pay sales tax to the state on the total amount of sales made by the merchant during each day's sales. You can imagine that if the sales tax rate is 3% and a child buys a 10c piece of candy there is no way to collect the three-tenths of one cent. If you rounded down that meant that the merchant could not collect anything for the tax. If you rounded up the state was gaining 7 tenths of a cent on every 10 cent sale. You can see that if the merchant sold 100 pieces of candy he was loosing 30 cents a day in tax revenues to the state, so the token was born. This allowed the merchant to take 11 cents for the first piece of candy and give change back in mills. The next time you wanted to buy a 10c candy you could present the merchant with the 10c and a token and complete the transaction. This allowed the merchant to collect the sales tax on each transaction.

Congrats to drewlambert02 who got it right - and I have to say that Randall's entry was one of the funniest I've read in a while!